Radio Frequency Identification (RFID) is utilized in a variety of applications with RFID readers communicating with RFID tags for purposes of identification, location, tracking, and the like. In an exemplary RFID application, an RFID reader may be mounted overhead (e.g., ceiling mounted) relative to a plurality of RFID tags, such as in a retail environment, a warehouse environment, etc. The overhead configuration offers several advantages such as fewer physical obstructions, ease of access to wiring in a ceiling, tamper resistance, safety, and the like. Conventional antenna configurations may be utilized in overhead configurations but these conventional configurations have disadvantages.
For example, RFID ceiling reader antennas can be oriented in one of three ways—parallel, normal, or angular to the ceiling. In the parallel mounted configuration (e.g. slot antennas) or the normal configuration (e.g. dipole antennas) the peak gain is at bore sight, with the main lobe of the antenna radiation directed straight down to the floor/ground. In the angular mounted configuration (e.g. patch antennas, loop antennas, etc), the angle of mount is selected to get some control of the radiation pattern and direct the main radiation lobe to the target of interest. A problem in the above scenarios is that, as we move away from the peaking angle of the main lobe of the radiation pattern, the gain of the antenna begins to drop, ending up in minimal gain at an antenna null point. For RFID applications this null situation results in a requirement to install multiple RFID readers with antennas aimed at various angles to get a consistent and a high percentage RFID read coverage. However, the use of multiple readers not only drives the installation cost up but also does not result in a high percentage of correct tag reads in areas where the antenna gain falls from its peak.
Accordingly, there is a need for an RFID antenna apparatus and method overcoming the aforementioned limitations by minimizing the number of RFID reader systems (especially ceiling mounted) installed in a particular environment, while maintaining/increasing overall read accuracy and correct read percentages. It would also be beneficial to use optimized power (i.e. a high-gain/low power reader combination and vice versa, while reducing cost by utilizing an optimal number of RFID readers at that optimal power.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.